FIELD OF THE INVENTION
The invention relates to the field of process engineering, and concerns a device for the deposition of substances from a gas phase.
In the production of semiconductor components, CVD processes (CVD=chemical vapor deposition) are commonly used for applying layer structures to semiconductor substrates. In these CVD processes, a plurality of reaction partners are introduced into a reaction chamber of a reactor using a carrier gas. The reaction partners, also referred to as initial products or precursor compounds, may be fed to the reaction chamber via one or more feed lines. In addition, other gases, e.g. oxidizing agents (O.sub.2) or inert gases (N.sub.2, Ar) are usually introduced into the reaction chamber in order to dilute the reaction partners. The reaction partners and oxidizing agents introduced react with one another to form the desired layer. This takes place on the surface of a semiconductor substrate placed in the reaction chamber. By varying the initial concentration of the reaction partners, the stoichiometric ratio of the individual constituents of the layers which are formed can be adjusted. In the deposition of metal oxide ceramics, e.g. SrBi.sub.2 Ta.sub.2 O.sub.9 (SBT) or (Ba,Sr)TiO.sub.3 (BST), which are employed for memory applications in the semiconductor industry, the reaction partners or initial products predominantly consist of metal complexes which are in gas form at elevated temperatures. In order to prevent the unused initial products from reaching downstream pumps or the surroundings, downstream cold traps for collecting unused initial products are used in the reaction chamber. These are intended to remove the initial products as fully as possible from the gas flowing through the cold traps.
A deposition system of the foregoing type is described, for example, in U.S. Pat. No. 4,647,338 to Jan Visser. In the process disclosed there for the production of a semiconductor component, a CVD system consisting of a reaction chamber and a downstream cold trap are used. A disadvantage, however, is that in that system deposition of unused initial products can actually take place even before, i.e., upstream of, the cold trap, which may cause clogging of feed lines and the like.